Key Difference – PTFE vs. PFA
PTFE and PFA are abbreviations for two synthetic polymers, Polytetrafluoroethylene and Perfluoroalkoxy respectively. They are fluoropolymers and share most properties in common. The most commonly known and widely used fluoropolymer is PTFE; also known as Teflon and the brand name of PFA is Teflon PFA. The key difference between PTFE and PFA comes from the resins that are used to make the polymer. PFA is melt processable and more versatile than Teflon; however, PTFE has excellent properties such as less water absorbent and stand against weathering.
What is PTFE?
The commercial name of PTFE (Polytetrafluoroethylene) is Teflon; a fluoropolymer with advanced properties such as high chemical resistance, low and high-temperature capability, resistance to weathering, low friction, electrical and thermal insulation, and “slipperiness. However, mechanical properties of PTFE are relatively low compared to other plastics; but remains stable over a wide temperature range. Different techniques are used to fabricate PTFE resins to form parts; ram extrusion, screw extrusion, compression molding, and paste extrusion with an extrusion aid. Three basic steps are common in these all techniques: cold forming, sintering, and cooling.
What is PFA?
PFA (Perfluoroalkoxy) is a fully fluorinated, translucent polymer and is commercially popular as Teflon PFA. It is marginally flexible polymer material with a low friction coefficient and exceptional non-stick properties. Moreover, it is a strong and hard material that shows high resistance to stress cracking and does not react with nearly all chemicals and solvents. In addition, PFA possesses a good temperature tolerant capacity and can be used in both high and low-temperature conditions. Its dielectric constant is excellent and chemical stability is also very high.
In producing PFA, it is melted and processed at very high temperatures; therefore it is extremely difficult to mold the PFA resin. Due to this fact, it is highly crystalline, viscous and extremely shear sensitive.
What is the difference between PTFE and PFA?
Structure:
PTFE: The PTFE has the repeating unit of -C2F4-, it contains only carbon and fluorine atoms.
PFA: The repeating unit of PFA polymer is given in the below. All the carbon atoms are fully fluorinated, and two carbon atoms are bonded together via an oxygen atom (-C-O-C).
Properties:
PTFE: PTFE is a hydrophobic synthetic polymer with a low friction coefficient. It has excellent thermal and electrical insulation properties. It has high-density value and cannot be melt processed. To form required shapes, it needs to compress and sinter. Its mechanical properties are comparative to with other plastics; however mechanical properties can be enhanced by adding fillers.
PFA: PFA is known as a flexible polymer with excellent chemical resistant and temperature tolerant properties. However, it is less heat resistant than PTFA. It has good dielectric properties, and the dielectric constant is equal to 2.1.
Applications:
PTFE: Teflon is popular as a non-stick coating in cooking pans and other modern items of cookware. It is also used in containers and pipes when handling corrosive and highly reactive chemicals due to its non-reactive properties. The other common application of PTFE is the use of as a lubricant to reduce friction in machinery.
PFA: PFA is commonly used to produce plastic laboratory equipment since it is optically transparent, flexible and chemically resistant to nearly all chemicals and solvents.It is also commonly used for tubing in handling critical or highly corrosive processes. In addition, PFA is used as sheet linings for chemical equipment, because it can use as an alternative for more expensive alloys and metals as a carbon steel fiber reinforced plastics (FRPs).
Image Courtesy:
1. Teflon items By Cjp24 (Own work) [Public domain], via Wikimedia Commons
2. “Pfa tubing“. [CC BY-SA 3.0] via Wikipedia
